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    Radiation Fog and Freezing Fog - Wilmington, Ohio


    Photographer's Description: Within a thick bank of fog, the WSR-88D radar is barely visible from just 270 feet away. The dim sun, low on the horizon, attempts to shine through.

    Photographer Andy Hatzos, NWS Wilmington
    Date taken December 6, 2007
    Location Wilmington, OH (Clinton County)     map
    Event Radiation fog

    Additional notes
    This photo shows radiation fog, which usually develops late at night and early morning when the ground radiates heat into the atmosphere (hence the name), causing the air near the surface to cool off rapidly.  If enough moisture is in place, the temperature will eventually drop to match the dewpoint temperature, causing moisture in the air to condense and form fog.  Clear skies and calm winds are usually needed for this to happen.   Click the link below to see atmospheric conditions which favor radiation fog.

    Since radiation fog is driven by the temperature near the ground, it is usually shallow.  It can range from about a thousand feet in depth to just a few feet off the ground.  Valleys are particularly prone to this type of fog since they are protected from the wind and cool off faster.

    On this particular day, the temperature was well below freezing which caused the fog to deposit ice crystals on objects (see link below).  This phenomenon is referred to as freezing fog.

    Safety Note: 
    Radiation fog can be very localized which presents a hazard to drivers.  While prevailing visibilities may be nearly clear, they may drop to near zero in a matter of seconds when a car enters an area of dense fog.  This may cause a driver to brake hard and increase the risk of getting rear ended (a common cause of fog-related accidents).  For this reason, it's always important to keep a safe distance between you and the car in front of you when radiation fog is present, even when visibility is clear.

    Related NWS Product:  Dense Fog Advisory Freezing Fog Advisory

    See ice which was
    deposited on objects


    See atmospheric conditions
    which favor radiation fog




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